From German patent document (Open Application) DE-OS No. 28 51 551 and other publications, it is known to provide a spindle press which comprises a press frame or support, a spindle rotatable on this support and having a threaded portion, a ram provided with a nut coupling the ram with the spindle and means, e.g. a piston-and-cylinder arrangement or jack for effecting a return stroke of the ram relative to the press support.
It is also known, when such a return stroke jack is provided, to also utilize a return stroke damping device which is effective to prevent the generation of a sudden shock when the ram reaches its return limiting position.
As noted, the spindle is coupled by a spindle nut to the ram.
In such systems in which a lubricant is provided, the ram can be formed as a hollow structure within which the lubricant is displaced by the relative movement of the ram and the spindle with the flow of lubricant between the end of the ram and the end of the spindle being controlled by a throttle to ensure that the lubricant will effectively pass between the surfaces of the internal thread of the nut and the external thread of the spindle.
The lubricant thereby obtains, via the throttle arrangement, a sufficient back pressure to ensure lubrication of the slidably engaging surfaces. This lubrication of the thread coupling the spindle to the ram in such prior art devices is the exclusive purpose of the throttle arrangement.
Consequently, where a return stroke is provided, e.g. by jacks in the manner described, a separate arrangement has been utilized for damping or slowing the return stroke at least toward the end of this stroke.
In other words, to damp the return stroke of the ram, a separate return stroke damping device was provided, utilizing conventional-pot dampers externally engaging or coupled with the ram and braced against the press support. This damping cylinder is positioned to become effective just before the ram reaches its upper deadpoint position.
Experience has shown that with rapid cycling of the press, these damping cylinders become unduly heated, thereby reducing their useful life and requiring maintenance expense and down time for the apparatus.
Furthermore, the setting of the upper deadpoint position and the setting of the damping cylinders requires separate means, thereby increasing the complexity of the apparatus.